1. Technical Field
The present disclosure relates to the electronics sector. More in detail, the present disclosure relates to a method for manufacturing a semiconductor material wafer.
2. Description of the Related Art
A semiconductor electronic device, either an Integrated Circuit (IC) or a power device, is a circuit whose components are directly fabricated in a semiconductor material substrate. The substrates of the great majority of the ICs presently available on the market are obtained from silicon (Si) wafers.
Recently, silicon carbide (SiC) wafers have been developed. Compared to silicon, silicon carbide has different chemical-physical properties, at least in part due to the different band gap value (indeed, silicon carbide has a band gap higher than that of silicon). For example, silicon carbide has a breaking voltage higher than that of the silicon, and it is thus an optimal material for manufacturing electronic devices for power applications, since a wafer (and, thus, a substrate for an IC) formed in silicon carbide is capable of managing voltages of relatively high values even with a relatively thin thickness. Moreover, using a silicon carbide wafer is particularly advantageous in all the electronic fields requiring the managing of high frequency signals.
Silicon wafers are typically formed in pure monocrystalline silicon. A known manufacturing process for generating wafers of this type is the so-called “Czochralski growth process”, which provides for introducing a monocrystalline silicon seed within a mass of melted silicon, and the gradual extraction of the seed from the melted silicon together with a slow rotation of the seed itself.
The presently employed techniques for growing a silicon carbide crystal are very complex and expensive. Because of its peculiar physical features, a silicon carbide wafer cannot be manufactured with the methods used for manufacturing silicon wafers. Since silicon carbide is a material which directly passes (sublimates) from the solid phase to the vapour phase, without passing from any liquid phase, the Czochralski growth process cannot be used, since this latter process just requires that the seed is inserted in a melting of the desired material.
Silicon carbide may occur in a number of different chrystallographic structures (polytypes). Among the number of polytypes, the most common are the cubic polytype (3C polytype), the hexagonal polytype (4H and 6H polytypes), and the rhombohedric polytype (15R polytype). Presently, by complex and expensive processes it is possible to manufacture silicon carbide wafers of the 4H and 6H polytypes having diameters not higher than four inches starting from the corresponding crystal obtained by a sublimation process. Such processes provides for cutting the ingot in slices, lapping, polishing of one of the two faces and then epitaxial growth.